Not sure if the GBI handicap system works the same way as the GHIN, but the latter takes the last 10 rounds played, I believe, and throws out the low and high scores posted in that window in adjusting ones index. This year, so far, the majority of my rounds have been in the high 80's and low 90's. I've had a couple rounds in the low 100's and I've shot as low as 84. Thus, I'm all over the map. I know a lot guys lout there like me that are erratic weekend warriros. I'm currently indexed at an 11.8, which is down from a high of 14.7 two years ago. The majority of my rounds are casual with members from my club, family members or frriends (guests), but I take pride in playing my best golf regardless of the situation and do my best to post a legitimate score within the confines of the GHIN structure.
While I only play in a few club tournaments throughout the year, I do partake betting games on some of my rounds just so there is something at stake to be gained or lost. I consider those "competitive rounds" even though they're non-tournament. That said, even when money is on the line putts are given routinely within 3' at most. If say a 3' or 2' putt is on a slippery downhill slope, they're not given as generously and more often than not are putted out. If I'm playing by myself, I won't give myself anything outside of 3' as those putts make for good practice during events or tournaments where you're required to make them.
I'm not sure what I'm trying get at here, as there are all fairly random thoughts, but I guess I'm hoping to shed light on how things are done typically in the U.S. in establishing one's handicap index and perhaps start a debate on what consitutes a competitive round, vs. casual, as I feel it extends beyond just tournaments - especially when there's money on the line.